The proposed research is a three-year investigation of the zoonotic cycle of cutaneous leishmaniasis in Texas. The long term objective is understanding of the epidemiology of cutaneous leishmaniasis in the United States, including mechanism of transmission, human risk factors, and dynamics of the enzootic cycle. The study will test the following hypotheses: I. The southern plains woodrat (Neotoma micropus) is the reservoir of Leishmania mexicana in Texas. II. Lutzomyia anthophora is the vector among the woodrats. Ill. Change of prevalence of L. mexicana in N. micropus is highly correlated with change of abundance of the sand fly, L. anthophora. A trap-release-recapture study of a population of N. micropus will monitor the seasonal change in prevalence of L. mexicana at a focus where transmission to a human is known to have occurred and prevalence in the woodrats is 50%. Woodrats will be screened for Leishmania by culture in Schneider's Drosophila medium supplemented with fetal calf serum, and PCR. Isolates will be characterized by enzyme analysis. The density and spatial distribution of the woodrats will be mapped using a Geographic Positioning System and a Geographic Information System. Seasonal changes in density and spatial distribution will be monitored. Population characteristics that influence the role the woodrats play as a reservoir, including mortality, natality, sex ratio and sand flies and dispersal, will be studied. The density, spatial distribution, and sex ratio of sand flies (Lutzomyia sp) associated with the woodrats will be monitored bimonthly for three years, using light traps, funnel traps, sticky paper and aspirators. Sand flies will be screened for Leishmania. Wind speed, wind direction, temperature, relative humidity, atmospheric pressure and precipitation will be continually monitored and correlated with sand fly population dynamics. The temperature and relative humidity within rodent burrows will also be monitored, and environmental conditions in burrows from which sand flies have been collected will be compared with those from which no sand flies are collected. The correlation between sand fly abundance and prevalence of infection in the woodrats will be tested, as will the correspondence in spatial distribution between infected woodrats and areas of peak sand fly occurrence. A model of transmission of L. mexicana among N. micropus will be field tested.